PROJECT 4 : REAL-TIME OPTICAL DIAGNOSTICS OF TISSUE FOR PDT DOSIMETRY AND TREATMENT CHARACTERIZATION The underlying premise of the proposed research is that clinical photodynamic therapy (PDT) dosimetry is limited, and that useful, minimally invasive optical instrumentation can be developed for in-situ dosimetry and treatment assessment based on measurement of tissue optical properties, tissue hemoglobin and drug concentration, tissue blood oxygen saturation and tissue blood perfusion. Over the past five years we have built and validated new experimental tools for this purpose, and we began exploration of their potential in animal models and human tissues during clinical PDT. Highlights of this work included the discovery of predictive correlations between PDT treatment efficacy, average blood oxygen saturation and blood flow in radiation induced fibrosarcoma (RIF) mouse tumor models. In addition we initiated optical property measurements in the clinic during intraperitoneal (IP) surgery. Our new aims derive from this experience. We will upgrade our instrumentation for clinical and animal model measurements to gather more macroscopic tissue information in-situ with greater speed and fidelity. More importantly, our scientific emphasis will shift to explore the potential of these tools to characterize tumor microenvironment brought about by biological targeting, and to develop dosimetric measures for PDT in animal models with and without biological targeting (with Project 3);a byproduct of these studies will be correlation studies of macroscopic variables with microscopic variables from immunohistochemistry. Finally, in collaboration with Projects 1 and 5 we will assess dose heterogeneity, tissue hypoxia, and blood flow in human tissues (normal and cancerous) during ongoing human IP and pleural clinical trials. We anticipate this quantitative information will take us further towards rapid, minimally invasive, in-situ optical diagnostics for PDT.